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64 The PCB Magazine • April 2017 Introduction Yes, it is annoying, even critical. Your cus- tomer returns product to you complaining about poor adhesion of plated copper to the surface. So what is the genesis of this defect? Is it electroless copper peeling from base laminate copper? Or is it electrolytic copper peeling from the electroless copper? One can experience cop- per peelers in pattern plating, panel plating or in electroless copper. Peeling can be seen on the conductors, within the PTH or in the microvias. Thermal excursions will exacerbate the problem as thermal stresses will increase the opportunity for one layer of copper to separate from anoth- er. As is often the case, separation of the copper from the post interconnect (aka interconnect defect) is considered peeling. However, I have presented ICD issues in previous columns, so this month the focus is on copper-to-copper peelers. Electroless Copper Peeling First, one must consider achieving good electroless copper-to-copper foil adhesion. One must start with a copper foil surface that is free from oxides, soil greases and other organic ma- terials. In addition, a micro-etching solution, whether it be persulfate or peroxide-sulfuric acid-based, should be used to ensure a clean and active copper surface that will provide suf - ficient surface roughness to promote and en- hance adhesion of the copper to the surface. Not to be forgotten is the need to get solid bond of the electroless copper to the innerlayer copper (post innerconnect) and to the capture pad of a blind via. In previous columns, I described several reasons that electroless copper could separate from the foil copper, copper interconnect and/ or copper capture pad. One such cause is the use of a particular type of cleaner-conditioner by Michael Carano RBP CHEMICAL TECHNOLOGY Copper-to-Copper Peeling TROUBLE IN YOUR TANK

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